BELL RINGER 1/7/16
• What special characteristic/feature would you only
find in sedimentary rocks?
IGNEOUS ROCKS
• Igneous rocks form as a result of cooling and
solidifying of rock material that was once molten.
• Lava: Molten rock material on earth’s surface
• Magma: Molten rock material inside of earth
• Igneous rocks are classified based on where they
formed
• Intrusive (Inside of Earth) – underground from
magma
• Examples:
Granite
Peridotite
Pegmatite
Gabbro
• Extrusive (Exited Earth and is now on the surface) –
at the surface from lava
• Examples:
Basalt
Rhyolite
Pumice
Scoria
FORMATION OF IGNEOUS ROCKS
• Solidification: Changing from a liquid to a solid
• Crystallization: Liquid to solid that causes crystals to
form
COOLING RATE
1. Slow – magma cools slowly underground. This give
crystals a chance to grow, resulting in larger
crystals.
COOLING RATE
2. Fast – lava cools quickly at the surface because it
is exposed to air and water****. This doesn’t allow
crystals to grow, resulting in small crystals.
•
**If cooling rate is really fast, no crystals grow, resulting in
a glassy texture.
RELATIONSHIP BETWEEN COOLING
RATE AND CRYSTAL SIZE
C
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Cooling Rate
IDENTIFYING IGNEOUS ROCKS
1. Determine Texture
• Coarse- Minerals visible to the naked eye
• Examples: Granite, Pegmatite, Gabbro
• Fine- Need magnification to see minerals
• Examples: Basalt, Rhyolite, Andesite
IDENTIFYING IGNEOUS ROCKS
2. Use grain size to determine texture
IDENTIFYING IGNEOUS ROCKS
3. Check color and density for composition
IDENTIFYING IGNEOUS ROCKS
4. Use chart for mineral composition
• http://www.ck12.org/book/CK-12-Earth-ScienceConcepts-For-Middle-School/section/3.8/
• Lava Flow GoPro
• Lava entering the ocean
• Smart or not so smart?